To fully understand how information is processed in complex cell circuits, we need techniques able to specifically target and control the activity of the elements involved, including astrocytes. Currently available tools like optogenetics and chemogenetics affect the entire astrocytic population, making it difficult to target specific subsets. This lack of specificity hinders our understanding of the role of astrocytes in behavior.We present a tool to translate the activity-mediated calcium signals of astrocytes into gene expression in a light-dependent manner, i.e. AstroLight. Using AstroLight in parallel with electrophysiology, pharmacology, fiber photometry and behavioral techniques, we demonstrate mice astrocytic involvement in motivated behaviors of the Nucleus Accumbens (NAc). First, we designed AstroLight vectors, validating their expression after viral infection. Then, using fiber photometry we monitored in vivo the astrocyte calcium dynamics in the NAc, demonstrating their involvement during a goal-directed behavioral task. Afterward, we used AstroLight to express channelrhodopsin (ChR2) in the active astrocytes related to reward consumption or exploratory behaviors. Three-dimensional quantification of the ChR2/AstroLight ratio across the NAc revealed astrocytic ensembles related to these different behavioral features. Finally, we modulated those ensembles through optogenetic stimulation, showing that activating the astrocyte ensemble related to a specific reward recalls the direction of behavior towards that precise option.Our results show AstroLight as a powerful tool to study astrocyte-neuron interaction’s function with precise spatial and temporal control and reveal that astrocytic ensembles can impact neuronal activity and shape behavioral responses positioning them as relevant components of the circuit.